The antibody levels against the novel coronavirus (SARS-CoV-2 virus) remains at high levels for at least nine months, whether symptomatic or asymptomatic infections, based on the data analysed from an Italian town.
“Researchers from the University of Padua and Imperial College London tested more than 85 percent of the 3,000 residents of Vo’, Italy, in February/March 2020 for infection with SARS-CoV-2, the virus that causes COVID-19, and tested them again in May and November 2020 for antibodies against the virus,” the Imperial College London said in its website on Monday.
The study was published in the journal Nature Communications, an open access journal, on Monday. As per the team’s findings, 98.8 per cent of the residents that were found Covid-19 positive in February or March 2020 were found with detectable levels of antibodies in November 2020. The team used three assays, tests that detect antibodies that respond to different parts of the virus. “The results showed that while all antibody types showed some decline between May and November, the rate of decay was different depending on the assay,” the Imperial College London said.
Meanwhile, the antibody levels were found to have increased in some people, suggesting potential cases of re-infection by the virus and providing a boost to the immune system.
“We found no evidence that antibody levels between symptomatic and asymptomatic infections differ significantly, suggesting that the strength of the immune response does not depend on the symptoms and the severity of the infection,” the lead author of the study Dr Ilaria Doreigatti, from the Imperial College London said. “However, our study does show that antibody levels vary, sometimes markedly, depending on the test used. This means that caution is needed when comparing estimates of infection levels in a population obtained in different parts of the world with different tests and at different times” the author further said.
The infection status of household members was also analysed to estimate how likely an infected person is to pass on the infection within the household. A probability of about one in four that the virus is transmitted within a household. It also showed that most transmission (79 per cent) is caused by 20 per cent of infections.
According to the team, the finding confirms that the majority of infections doesn’t generate further infections and only a minority of the infections caused a large number of infections. It also showed that physical distancing, limiting the number of contacts and wearing face masks continue to remain important measures in reducing the risk of transmission even in highly vaccinated populations.
The data also showed that in the absence of case isolation and short lockdowns, manual contact tracing alone would not have been enough to suppress the pandemic, the Imperial College further said.